Simplify. Rewrite the expression in the form $9^n$. $\dfrac{9^{-3}}{9^{12}}=$
Recall that $\dfrac{x^n}{x^m}=x^{n-m}$. $\begin{aligned} \dfrac{9^{-3}}{9^{12}} &= 9^{-3-12} \\\\ &= 9^{-15} \end{aligned}$